April 30, 2011

Is there intelligent life in the universe? And if so, what will our first encounter with extraterrestrials yield? Check out this click from the BBC special The Search for Life: The Drake Equation that seeks to answer some of these questions.

April 27, 2011

After Areios unthawed from a 130-million-yer long period of worldwide glaciations, the planet looked remarkably different from before the deep freeze. The atmosphere was made up of reduced gases like water vapor carbon dioxide, hydrogen sulfide and methane, and carbonyl sufide. Gases like water vapor, carbon dioxide, carbonyl sulfide and methane are powerful greenhouse gases that raise the average temperature of the planet. On Earth, an excess of these gases generated by human industry are widely believed to cause destabilizing climate change on Earth. On a planet like Areios, this increase in greenhouse gases is a boon because it melted the ice that straddled the tropical regions of the world and caused sea levels to rise, washing organic salts and other chemicals locked in the continental crust into the sea, making a frothy brew of organic chemistry that would form the basis for the earliest life.

Deep at the bottom of the ocean, there are volcanic vents that eject boiling water laced with metals; on Earth these environments are heavily populated with life. Meter-long tubeworms powered off of bacteria in their guts that eat the dissolved gases in the water. Translucent crabs and squids feed off of the see-through krill that are the basis of this underwater ecosystem. Researchers believe that the bacteria found in these vents are among the oldest known organisms on Earth. Similarly, these vents are the wellspring for the first life on Areios. Iron-bearing minerals at the bottom of the ocean serve as catalyst for complex organic molecules to form. Over time as a primitive form of natural selection takes place the more robust molecules that replicate with greater efficiency win out over organisms that can’t replicate fast enough or fall apart too easily. And over time, those molecules that could replicate the best would dominate the environment. It’s easy to imagine that the first life forms on earth were bare-bones, single-celled proto-cells that could replicate and do not much else.

Over time, those that developed a more robust metabolism could survive times when the organic molecules that they fed on were scarce. And as natural selection kept on, the metabolisms of these early cells became more and more eclectic, with many different metabolic pathways being developed by their forms to exploit the energy around them. This allowed for greater biodiversity and minimized competition for the same resources. The early biology on Areios as well as on Earth formed these microbial mats; an entire ecosystem was enclosed in a single patch of pond scum, with some creatures emitting gases like methane or hydrogen sulfide and other creatures that could exploit these waste for their own metabolism, transforming that hydrogen sulfide into sulfur granules of sulfuric acid and breaking that methane down into hydrogen gas that bubbled out of seas.

At first the earliest life was confined to a single area, but pressure for resources like the organic molecules that served as food, life forms began to spread out around the globe, filling up new unexplored niches and evolving to meet the new conditions. Eventually, every niche around the world was filled up and there was nowhere else for these life forms to head to. And from that point on, the competition for resources intensified and the less resilient creatures were muscled out of their niches. In perhaps the greatest phenomena of the time, predation arrived on Areios soon after the niches of the world were taken. Bigger organisms no longer had to engulf free-floating molecules in order to feed; they could engulf their free-floating cousins, too. This is entirely because of biological compatibility; organisms that ingest free-floating molecules incorporate nutrients into their metabolism and other organisms with the right cellular machinery can eat those cells and gain their nutrients from the primary producer. This was one of the first major events in the history of life on Areios and predation will lead to yet another milestone in the history of life; the appearance of eukaryotic cells from what is called endosymbiosis. But more on that later…

April 23, 2011

The study of origin of life (pg. 4) on Earth is still a perplexing subject for academia because its unlikely scientists will never definitely be able to confirm or deny any theories about our origin simply because we have no evidence to support or refute any claims. While there can never be an answer to any of these questions about where we came from, theories, speculations, and wild guesses abound from scientists who study the matter. Ever if we do manage to one day build life from scratch, we will never be able to prove that life on Earth was formed in the same process as a manufactured cell. Most scientists agree that life arose from the chemical evolution of organic molecules and that a primitive selection process favored self-replicating organic systems that could reproduce themselves more efficiently. We’ll highlight a few of the most interesting theories and compare the merits of these ideas. Eventually these processes would lead to something we would consider to be alive; something that can no longer be considered solely a chemical reaction, but start to resemble a biological system.

A researcher from the University of Glasgow advanced a kaolin-clay hypothesis for primitive life. His theory goes that the earliest forms of life were made from self-replicating silicate crystals; not truly alive, but showing a remarkable level of organization. These clay crystals could have been the precursor to all organisms and could have shown a rudimentary form of metabolism and self-replication. Kaolin clay forms in a specific lattice arrangement that is preserved even as these minerals grow and the right minerals dissolved in solution speed up the rate at which these crystals form in the presence of water. This diet of dissolved minerals in water could be thought as analogous to metabolism in a living creature. The increasing complexity of the structures of these crystals served as the mold for increasingly complex organic compounds. Further research revealed that when a certain crystal is sliced in half and dipped in an aqueous solution, the mineral is that regrows to complete the rest of the crystal and will copy the same imperfections of the parent crystal, while forming new imperfections along the way. This could suggest a weak form of natural selection and a primitive form of heredity; because imperfections in the crystal get carried with each copy to the next, there is said to be some form of inheritance of characteristics. And because some crystals would grow faster than others based on the mineral water available to them and the robustness of their crystal lattice, more stable minerals in favorable environments would grow faster than those in poor environments, and dominate the environment.

Some researchers have posited that the origin of life suggests that a primitive cell membrane appeared first and engulfed the cellular machinery that developed later. Others suggest that the cellular mechanisms had to have come first and that their vessel was created later one. Scientists studying the origin of life are loosely divided into two camps; those who believe metabolism occurred first, or those who believe genetics were developed first. So the research in this field focuses on two different approaches (pg. 2) to this problem; some start from scratch and try to build a self-replicating entity while others take a top-down approach and strip a living cell of all but the most necessary machinery in an attempt to figure out what mechanisms working within the cell are the most fundamental and hence the most primeval.

Researchers looking at Stanley Miller’s research into the origin of life have wondered if the prebiotic environment interacted with the geology of the early Earth. After researching common minerals, they found that the mineral borax can stabilize the ribose sugar in RNA, allowing significant quantities of RNA accumulate in the environment in levels useful to biology. As the authors suggest, this could alter our understanding of the origin of life because borax doesn’t appear in a warm little pond like Darwin suggested, or even in a hydrothermal vent like some modern researchers posit; it places our origin in the arid environment because borax is a salt found in deserts. In Peter Ward’s book Life As We Do Not Know It, Ward cites speculation by some researchers who believe the ingredients for life or even life itself may have come from the drier planet Mars, which would have mirrored Earth in some ways around the time that life was forming on our planet. If the chemical ingredients for life or even a partially-assembled cell arrived on Earth from Mars via a comet impact, it could have a profound impact on our understanding of life; if we can partially trace our origins back to Mars, does that make us Martians?

April 20, 2011

Just how did life begin on Earth? While there is no one satisfactory answer to this question, theories abound with ideas that suggest the role of ice crystals, clays, or borax could have given life a start on Earth. Check out these articles on the origin of life.

April 17, 2011

We’ve discussed the formation of the planet Areios, the stellar characteristics of the star it orbits, its interactions with its three moons and the Alkyoneus gas giant. We’ve covered the composition of the crust, and the presence that liquid water plays in plate tectonics, which is the mechanism that regulates the atmosphere’s composition. All of these factors have been leading up to the sole reason why this thought experiment; these factors lead to an environment conducive to the origin of life. A phenomenon so rare that for the majority of human existence we could not even fathom the concept that life could have arisen a second time on some other world, no matter how likely that possibility may be, given what we know about the enormity of the universe. Separated by 14 billion years of cosmic evolution, humans are connected to all living things in the universe by our distant relation to the first stars ever spawned after the Big Bang that spread the chemical means for biology to exist. Our discussion of Areios and the solar system it occupies will forever be changed by the presence of life. Starting with the most basic cells and climaxing with animal life, the many forms of Areia and its evolution through time will dominate this discussion of speculative biology.

The history of our understanding of the origin of life in Western thought begins with the book of Genesis in the Bible; the idea that life on Earth was created in just seven days was the undisputed paradigm for two thousand years. It wasn’t until later in the nineteenth century that the science behind chemical evolution began to arise with Charles Darwin’s writing. He conjectured that all complex life alive today evolved from a simpler form until he reasoned that all life arose from a single common ancestor that was spawned in what he described as a “warm little pond” somewhere. But the greatest breakthroughs on this subject came with the research of J.S. Haldane and Alexander Oparin. These two scientists independently worked on theories of biochemistry that suggested life wasn’t an intrinsically magical property; cells were a very complex set of specific inorganic chemical reactions, all occurring within the boundaries of a cell. In this understanding, cells were bags of chemical machinery that could self-replicate under the right conditions. These scientists believed that the early environment on Earth was conducive for a primitive biological system to spawn. The Urey-Miller experiment in 1948 by Stanford scientists Stanley Miller and Harold Urey experiment went one step further to simulate the conditions of early Earth that would have led to the creation of life.

The basic building blocks of biochemistry like carbon monoxide, water, ammonia, and methane were heated in a glass tube and sent through a battery of shocks before allowed to condense in a test tube on the other end. The results were spectacular; the pair of scientists discovered that given the right ingredients and the right conditions, amino acids, the building blocks of the proteins could form from such simple processes. As this experiment was repeated, some scientists began to question the validity of the assumptions made; some questioned the composition of the atmosphere assumed in the experiment wasn’t realistic. When Miller passed away in 2007, researchers unearthed the apparatus he used and repeated the experiment, this time using more sensitive instruments to detect chemicals and a more accurate understanding of the environment at the hypothesized time of creation; scientists were astounded by the presence of even more amino acids produced. Even more surprising was when researchers located a vial that contained the results of another experiment that Miller kept from the world for over 25 years. He mixed ammonia and cyanide, but immediately froze the chemicals at over -100 Fo. Scientists opened that sealed vial and analyzed the results to find that despite the fact that chemical reactions proceed at a snail‘s pace at those frigid temperatures the air bubbles trapped within the ice made an ideal test tube for amino acids and nucleotides to form.

Astronomers have found complex organic molecules floating out in nebulas or in the icy tails of comets; since then, some researchers believe that the ingredients for life may be delivered ready-made to the Earth by impacts. Others believe that freeze-dried cells might be able to hitch a ride on a meteorite from some other world only to survive the re-entry into the atmosphere where these spores would colonize some barren but habitable world. These processes called panspermiamay seed the universe (or at least neighboring planets) with extraterrestrial life. There is some debate among scientists if this process of transferring spores from one world to the next has happened in our solar system or if the idea is even possible. In any case, research points out that even the simplest organic molecules in our body can be created abiotically. This alone suggests that life need not form from some supernatural process directed by an omnipresence god, but that the origin of life could be explained entirely by organic chemistry and eventually biocatalysis.

The Urey-Miller experiment first presents experimental evidence of chemical evolution leading to the creation of life on Earth.

April 5, 2011

Areiosan geology varies markedly over time; early crust of the planet is dominated by hydroxide minerals that formed when rocks come in contact with superheated water. In this process called serpentination, water comes in contact with certain rocks; it forms these hydroxide minerals and hydrogen gas, which can later form methane in a reaction with organic molecules. Over time, this hydroxide mineralogy would be replaced by sulfide minerals. Sulfur is a reactive element that tends to replace carbon in some molecules, just as any oxygen at the time would obliterate any methane in the atmosphere. Although methane is quickly broken down into carbon dioxide, the early planet was producing more methane abiotically than could be destroyed naturally. This helped to keep the early planet from freezing over under a lukewarm Hemera. When Areios’ crust was forming at the beginning of time, the planet glowed like an incandescent light bulb for millions of years until it cooled down enough for the crust to solidify and water to form on the surface. As water vapor condensed and rained down on the planet, the temperatures began to cool.

At the time, the atmosphere was heavily laced with sulfur compounds, and this mingled with the water vapor in the atmosphere to create acid rain. Because sulfuric acid has a higher boiling point than water, sulfuric acid was the first to rain down on the planet, eating away at the surface and acidifying the oceans. Once the atmosphere was purged of sulfur compounds, the atmosphere became less choked with smog. On Earth, sulfur compounds spewed from volcanoes block the Sun’s rays, causing an overall cooling effect. Once the sulfur was done raining down from the sky, solar radiation poked through the atmosphere and heated the planet up a little bit, but it wouldn’t be enough to keep water vapor in the atmosphere, generating a greenhouse effect. Next in the progression, water condensed and rained down on the planet, covering its surface with pools of toxic seas. With this atmosphere mostly made of nitrogen, hydrogen, helium, noble gases the water vapor and carbon dioxide churned out by volcanic activity wasn’t enough to keep the planet warm. The oceans froze from the poles outward as the planet lurched out its rotation, thanks to the gravity of Alkyneous as was plowed back into deep space by the gravity of Hemera. With this Milankovitch cycle allied with the drastic cut back in greenhouse gases, the planet was fast becoming an iceball. Carbon dioxide is more soluble in cold waters, so the falling temperatures sped up the process of scrubbing carbon dioxide out of the air. Soon it got so cold worldwide that carbon dioxide even began to condense into dry ice, marbling the ice water now dominating the surface. With the atmosphere all but scrubbed of water, sulfur, carbon, Hemera shone brightly on the planet for the first time since its creation. But with ice reflecting most of the light back out into space, Areios stayed cold for quite some time.

But eventually, the planet swung back into an orbit close enough to Hemera that allowed carbon dioxide frozen on the surface to thaw out. With all of the ice on Areios pressing down on the tectonic plates, continental drift slowed to a halt. And because the shifting of tectonic plates provides substrate for carbon dioxide to react with rocks to form carbonate minerals, carbon dioxide and especially methane began to build in the atmosphere. The thick layer of ice on Areios’ surface conceals an active interior; the mantle is still radiating heat underneath miles of ice, spewing out dark colored rocks and oxygen-rich minerals kept safe from the rest of the environment by a thick coating of ice. With Hemera shining brighter on the planet than ever before, with carbon dioxide levels ratcheting up with no tectonic cycle to stop its progress, and with oxygen accumulating as oxidized minerals in the mantle and kept under miles of ice, Areios was primed for a great thaw.

First the tropics thawed, exposing dark colored continental rocks and raising sea levels. Then as more ice melted into lakes and seas, the liquid water absorbed heat as it exposed more surface area underneath receding ice. The plate tectonic cycle started back up, shuffling the continents into a supercontinent, creating vast expanses of shallow seas and driving ocean currents to spread the heat around to the poles as retreating back to all but the tiniest corners of the poles. With most of the oxygen safely trapped in the crust, methane and carbon dioxide reach record high concentrations and Areios returns from the deep freeze with a planet straddling ocean and an atmosphere primed for the creation of life. Oceans became saturated with carbon dioxide and other organic molecules that washed into the sea from the continents once new area of continental shelf become exposed to wind and water currents. The oceans became a veritable laboratory of organic chemical reactions and now that temperatures were on the rise, a lot of interesting chemistry was going to occur.

This is a depction of Areios covered from pole-to-pole with glaciers in an analgous Snowball period

April 2, 2011

Check out this animation of the Snowball Earth Hypothesis. This animation from Essentials of Geology by Stephen Marshak and Rita Leafgren shows the four proposed stages to the formation and destruction of Snowball Earth conditions: